| Abstract/Description or Keywords |
The Nechako River is one of the major tributaries to the Fraser River, affecting both its hydrology and its water quality. The headwaters of the Nechako River are located in the Nechako Reservoir drainage basin, and flows in the upper watershed are controlled by the Kenney Dam. The drainage area of the river at Prince George is 46,000 km2. Nechako River water quality is influenced by the water quality of the Stuart, Nautley, and Chilako rivers. Water uses for the Nechako River at Prince George include irrigation, livestock watering, primary and secondary-contact recreation (i.e., swimming and boating), drinking water with partial treatment, and use by aquatic life and wildlife. CONCLUSIONS: • The Nechako River at Prince George had occasionally high turbidity values, generally as a result of spring freshet or high precipitation. Treatment to remove turbidity is needed before using the water for drinking. Peak turbidity values seem to be higher in recent years. • When drinking water and aquatic life guidelines were exceeded for metals such as aluminum, cadmium, chromium, cobalt, copper, lead, manganese, iron, silver, and zinc, there was a strong correlation with high turbidity values, suggesting that these metals were in particulate form and therefore not biologically available. In addition, water treatment (e.g., filtration) necessary prior to consumption would remove the majority of these suspended metals from drinking water. • With reduced detection limits in recent years, concentrations of cadmium and silver generally have met guideline levels for aquatic life. The relation of measured values to high detection limits was a concern expressed in the last assessment that has been addressed. • Water temperatures exceeded the guidelines for migration to protect salmonids during most summers. • Fecal coliform concentrations met the objective (i.e., were within acceptable limits for water that undergoes partial treatment (e.g., filtration) plus disinfection prior to drinking). pH also met its objective. • Total organic carbon often exceeded the guideline for raw drinking water that will be chlorinated, and treatment to remove organic carbon and alternate disinfectants should be considered before drinking water use. • True and apparent colour data exceeded the aesthetic guidelines for true colour in drinking water. These values in excess of the guideline were related to turbidity. • High total and dissolved phosphorus levels are related to turbidity. RECOMMENDATIONS: We recommend that monitoring be continued on the Nechako River at Prince George. Water quality data collected at this site would be used to: • represent the water quality from the upper portion of the interior plain ecosystem, • show the cumulative effects of water from the Stuart, Nautley, and Chilako rivers on water quality and hydrology, • check attainment of water quality objectives established for the Nechako River, and • determine changes in the water quality of the Fraser River downstream from the Nechako River confluence. Water quality indicators that are important for future monitoring are: • flow, water temperature, specific conductivity, pH, • total dissolved phosphorus, total dissolved nitrogen, periphyton chlorophyll-a, • dissolved oxygen, fecal coliforms, and • true colour, turbidity, hardness, dissolved aluminum, total and dissolved copper, lead, nickel, and zinc. • Trihalomethane (THM) concentrations should be measured in treated drinking water supplies to ensure that the high levels of dissolved organic carbon are not resulting in high residual THMs after water is chlorinated for drinking. • The trivalent and hexavalent forms of chromium should be measured in the future, when the methods become available, to permit comparison to the aquatic life guidelines. |
